Lovrina- Let's see, just use anything. She is pathetic.
Snattle- Get some pokemon with average to above average stats. If they have low defence & special defence they won't last long.
Ardos- Finally, a bit of a challenge! Watch out for his snorlax, as it uses shadow end. Bring in some tanks, and use them on snorlax. Try grass and dark pokemon, like shiftry would be a prime option. Confuse them, as they hit hard.
Gorigan- He has earthquake on the wrong pokemon, so just bring a pokemon with high defence. Magmar works well, if you teach it protect, then you can just take out a pokemon with earthquake (I used khangeskan) to counter his.
Eldes- Easy. Some might disagree, but with the right pokemon you can catch all of them. First you need a sleeper with high hp. (Khangeskan again) Also, you need to have some pokemon with very uber high defence, as his marowak has a thick club and uses shadow end.
Greevil/XD001- I recommend masterball, but whittle it's hp down with about a level 50 electric pokemon or shadow lapras.
Greevil- 3 or 4 tanks will be good, snorlax, lapras and xd001 work. Get a special sweeper and a physical sweeper for the ones you don't want. Zangoose works well as a phys sweeper and Espeon is also a good choice for a special sweeper, as is lunatone or solrock.